Replacing the Fire Brick With Something Else

Freddy wrote:Well.... last I knew it would take nine inches of brick to make an insulation value of R-1. So, I wouldn't give too much thought to a firebrick causing heat loss. If it needs brick, give it to 'er!

Yeah, I should have looked into that .. Here's what I found at a quick glance on google.

Fire Brick - Very hard, very heavy, low insulating value brick, usually yellow grey in color with sharp corners. Discussed both by temperature rating and materials used which resist chemical attack. Usually available by each (instead of box) and may cost anywhere from $2-3 each to $27-40 each depending on material.

Sounds just exactly like the stuff I'm using.
Guess I won't wonder much further about it. Thank you..

Sunny Boy wrote:KS,
That's very much like the pot belly stove I used anthracite in (unlined) for about ten years. Like many of those small pot belly stoves, it leaked so much air at the doors, dampers, and grate shaker shaft opening, that it's tough to NOT have it glowing red.

Paul - did the anthracite burn and hold temp very well in that stove or did it just burn it all up to fast due to the air leaks?

Lee - for what it's worth, when I "double-lined" my Hot blast with fire brick the plenum temp was exactly the same vs fire-box temp after the first 24 hours.
I have a digital thermometer inserted into one of the 8" ducts from my Hot blast right where it goes into the plenum.There is about 5' of 8" duct from the stove to the plenum. When my over the door temp on my furnace is in the 495 to 525 degree range (that's where it likes to run for the first couple of hours after loading up) the air temp going into the plenum is between 154 to 158 degrees.
This is the same temp I was getting before I double lined with fire-brick.
I know that doesn't let you know what the temp would be like without the layer of fire-brick but it maybe helps with formulating a theory...

Thank you KY, your observation reinforces that the firebrick don't Block much heat. Not enough to make any drastic changes.

Lightning wrote:Thank you KY, your observation reinforces that the firebrick don't Block much heat. Not enough to make any drastic changes.

Fire brick makes a major difference. Hold your hand in a cast iron skillet on the stove and you wont hold it there for long. Replace the skillet with a fire brick of 1.25 thickness and feel the difference.

The best fire pot is the one that losses the least heat. The design that works best is the suspended pot that circulates the flue gas around it. Second best is the lined pot. First consideration is to burn the coal evenly and completely and the second consideration is to extract the heat. The best design is the one that separates those two functions of a stove as much as possible. An excellent fire pot could be built of stainless steel provide it is insulated by surrounding flue gas or something like ceramic felt.

franco b wrote:An excellent fire pot could be built of stainless steel provide it is insulated by surrounding flue gas or something like ceramic felt.

I agree 100% Franco.

Well said.

A nickle "superalloy" pot that has a thermal barrier applied on the inside with a thick crucible style ceramic liner, would be ideal.

Wether or not that would be economically viable in a production sense is another. However I know someone who is going to attempt it for his personal stove.

Lightning wrote:Well that's pretty interesting.. Since the belly was glowing red most of the time, it must have been yanking a serious amount of heat out of the burning coal bed. Did this inhibit the coal from burning as was suggested earlier?

Lee,
At the outer edges, it didn't burn the coal as completely to white ash as the range can. And that's with the pot belly having whatever advantage there is of a round firepot verse the rectangular firebox of the range.

Paul

Ky Speedracer wrote:

Sunny Boy wrote:KS,
That's very much like the pot belly stove I used anthracite in (unlined) for about ten years. Like many of those small pot belly stoves, it leaked so much air at the doors, dampers, and grate shaker shaft opening, that it's tough to NOT have it glowing red.

Paul - did the anthracite burn and hold temp very well in that stove or did it just burn it all up to fast due to the air leaks?
......................................

KS,

It leaked so badly that, even dampered down as tight as possible, it wouldn't hold a fire long enough to make it through the night. I sealed up the worst of the leaks around the doors and the shaker shaft opening using the old waxed paper and refractory cement trick. That helped for slowing it down to gain some measure of control that I could keep it below the glowing red stage if I wanted (I rarely did), and it would hold a fire through the night,... if I didn't sleep late.

However, the pot still lost heat to the point that it never burned the outer layer of coal to white ash as was well as my range can with it's original, one inch thick clay fire bricks - even in the corners where square cornered fireboxes don't do their best.

Paul

Paul

Thanks Paul!

Why should it be so important that coal around the edges of the fuel bed completely burn, anyways? Because it would insure that the most available oxygen entering the stove would be put to good use instead of slipping by the edges and going up the stack? I can see how this would be a detriment to efficiency. If this true then the big question is, would this lack of efficiency outweigh the benefits of extracting more heat at the fuel bed level by not using the bricks? It seems there would be a compromise to some extent.

Thank you for everyone's wisdom.
I find the differing opinions and their reasoning quite interesting.

Lee,
Two things.

First,...
The perimeter of any firepot or firebox holds a lot of coal. By not burning that large-percentage outer area as completely as possible, your wasting a lot of the potential heat in a load of coal.

Second,...
Remember that the firebox is only part of the system. Which would you rather have ,..... extracting more heat at the firebox, and the result is a loss of overall coal burning efficiency, and less TOTAL heat output, or burn ALL the coal more completely and get even more heat out later in the system ?

If you can extract heat efficiently after the firepot, then it makes more sense to burn the coal as completely as possible to get the most BTU's out of every pound. Feeling warmer at the firebox is not necessarily getting the max heat out of every pound of coal.

Paul

You know, when I began burning anthr. in the Vigll, I was dreaming of the best coal stove, the perfect one for my needs , so I began a long road of modifs and modifs.....till the day I got the Sunnyside. Then all my dreams came true and I forgot modifications.
Conclusion= don't change the fire bricks, change the unit

Just seems like there is some contradicting information. Seems to be that unlined is ok for some stoves but won't work for others. The only difference I'm seeing is round and square..